Sphingomyelin Synthase 1 Is Essential for Male Fertility in Mice

A new mutation of Sgms1 causes gradual hearing loss associated with a reduced endocochlear potential

Sgms1 encodes sphingomyelin synthase 1, an enzyme in the sphingosine-1-phosphate signalling pathway, and was previously reported to underlie hearing impairment in the mouse. A new mouse allele, Sgms1tm1a, unexpectedly showed normal Auditory Brainstem Response thresholds. We found that the Sgms1tm1a mutation led to incomplete knockdown of transcript to 20 % of normal values, which was enough to support normal hearing. The Sgms1tm1b allele was generated by knocking out exon 7, leading to a complete lack of detectable transcript in the inner ear. Sgms1tm1b homozygotes showed largely normal auditory brainstem response thresholds at first, followed by progressive loss of sensitivity until they showed severe impairment at 6 months old. The endocochlear potential was consistently reduced in Sgms1tm1b mutants at 3, 4 and 8 weeks old, to around 80 mV compared with around 120 mV in control littermates. The stria vascularis showed a characteristic irregularity of marginal cell surfaces and patchy loss of Kcnq1 expression at their apical membrane, and expression analysis of the lateral wall suggested that marginal cells were the most likely initial site of dysfunction in the mutants. Finally, significant association of auditory thresholds with DNA markers within and close to the human SGMS1 gene were found in the 1958 Birth Cohort, suggesting that SGMS1 variants may play a role in the range of hearing abilities in the human population.

Male infertility risk and plasma lipidome: a Mendelian randomization study

Background

In recent years, the decline in sperm quality in men has become a global trend. There is a close relationship between sperm quality and pregnancy outcome. There is a large body of literature supporting the role of plasma lipidome in male infertility, while the complex mechanisms between them and male infertility are still less clear. Systematic study of the causal relationship between plasma lipidome and MI can help to provide new therapeutic ideas and targets for male infertility.

Methods

In this study, we used a two-sample Mendelian randomization analysis based on Genome-wide association studies pooled data of 179 causal relationships between plasma lipidome and male infertility. We used employed the inverse variance weighted method as the main analysis to assess causality between exposure and outcome, in addition to MR-Egger, Weighted median as complementary methods, and tests for multiplicity and heterogeneity.

Results

We identified 13 plasma lipidome comprising 4 types of plasma lipidome that were associated with male infertility. Among these, 9 plasma lipidome were found to be protective factors, while 4 were risk factors. Notably, the largest proportion of these plasma lipidome were triglyceride types, with Sphingomyelin (d40:1) exhibiting the strongest association with male infertility.

Conclusion

These findings contribute to the current better understanding of male infertility and provide new perspectives on the underlying etiology of male infertility as well as prevention and treatment strategies. In addition, clinical trial validation is needed to assess the potential of these plasma lipidome as biomarkers.

Human sphingomyelin synthase 1 generates diacylglycerol in the presence and absence of ceramide via multiple enzymatic activities

Sphingomyelin (SM) synthase 1 (SMS1), which is involved in lipodystrophy, deafness, and thrombasthenia, generates diacylglycerol (DG) and SM using phosphatidylcholine (PC) and ceramide as substrates. Here, we found that SMS1 possesses DG-generating activities via hydrolysis of PC and phosphatidylethanolamine (PE) in the absence of ceramide and ceramide phosphoethanolamine synthase (CPES) activity. In the presence of the same concentration (4.7 mol%) of PC and ceramide, the amounts of DG produced by SMS and PC-phospholipase C (PLC) activities of SMS1 were approximately 65% and 35% of total DG production, respectively. PC-PLC activity showed substrate selectivity for saturated and/or monounsaturated fatty acid-containing PC species. A PC-PLC/SMS inhibitor, D609, inhibited only SMS activity. Mn2+ inhibited only PC-PLC activity. Intriguingly, DG attenuated SMS/CPES activities. Our study indicates that SMS1 is a unique enzyme with PC-PLC/PE-PLC/SMS/CPES activities.

Integrated fecal microbiome and metabolome analysis explore the link between polystyrene nanoplastics exposure and male reproductive toxicity in mice

Microplastics (MPs) and nanoplastics (NPs) are novel environmental pollutants that are ubiquitous in the environment and everyday life. NPs can easily enter the tissues and have more significant potential health risks due to their smaller diameter. Previous studies have shown that NPs can induce male reproductive toxicity, but the detailed mechanisms remain uncertain. In this study, intragastric administration treated mice with polystyrene NPs (PS-NPs, 50, and 90 nm) at 3 and 15 mg/mL/day doses for 30 days. Then, the fresh fecal samples were collected from those mice that the exposure doses of 50 nm PS-NPs at 3 mg/mL/day and 90 nm at 15 mg/mL/day for subsequent investigations of 16S rRNA and metabolomics according to significant toxicological effects (Sperm number, viability, abnormality, and testosterone level). The conjoint analysis findings indicated that PS-NPs disrupted the homeostasis of the gut microbiota, metabolism, and male reproduction, suggesting that abnormal gut microbiota-metabolite pathways may be important in PS-NPs-induced male reproductive toxicity. Meanwhile, the common differential metabolites such as 4-deoxy-Erythronic acid, 8-iso-15-keto-PGE2, apo-10'-violaxanthin, beta-D-glucosamine, isokobusone, oleamide, oxoadipic acid, sphingosine induced by 50 and 90 nm PS-NPs might be used as biomarkers to explore PS-NPs-induced male reproductive toxicity. In addition, this study systematically demonstrated that nano-scale PS-NPs induced male reproductive toxicity via the crosstalk of gut microbiota and metabolites. It also provided valuable insights into the toxicity of PS-NPs, which was conducive to reproductive health risk assessment for public health prevention and treatment.

Delivery of ceramide phosphoethanolamine lipids to the cleavage furrow through the endocytic pathway is essential for male meiotic cytokinesis

Cell division, wherein 1 cell divides into 2 daughter cells, is fundamental to all living organisms. Cytokinesis, the final step in cell division, begins with the formation of an actomyosin contractile ring, positioned midway between the segregated chromosomes. Constriction of the ring with concomitant membrane deposition in a specified spatiotemporal manner generates a cleavage furrow that physically separates the cytoplasm. Unique lipids with specific biophysical properties have been shown to localize to intercellular bridges (also called midbody) connecting the 2 dividing cells; however, their biological roles and delivery mechanisms remain largely unknown. In this study, we show that ceramide phosphoethanolamine (CPE), the structural analog of sphingomyelin, has unique acyl chain anchors in Drosophila spermatocytes and is essential for meiotic cytokinesis. The head group of CPE is also important for spermatogenesis. We find that aberrant central spindle and contractile ring behavior but not mislocalization of phosphatidylinositol phosphates (PIPs) at the plasma membrane is responsible for the male meiotic cytokinesis defect in CPE-deficient animals. Further, we demonstrate the enrichment of CPE in multivesicular bodies marked by Rab7, which in turn localize to cleavage furrow. Volume electron microscopy analysis using correlative light and focused ion beam scanning electron microscopy shows that CPE-enriched Rab7 positive endosomes are juxtaposed on contractile ring material. Correlative light and transmission electron microscopy reveal Rab7 positive endosomes as a multivesicular body-like organelle that releases its intraluminal vesicles in the vicinity of ingressing furrows. Genetic ablation of Rab7 or Rab35 or expression of dominant negative Rab11 results in significant meiotic cytokinesis defects. Further, we show that Rab11 function is required for localization of CPE positive endosomes to the cleavage furrow. Our results imply that endosomal delivery of CPE to ingressing membranes is crucial for meiotic cytokinesis.

Sperm Lipid Markers of Male Fertility in Mammals

Sperm plasma membrane lipids are essential for the function and integrity of mammalian spermatozoa. Various lipid types are involved in each key step within the fertilization process in their own yet coordinated way. The balance between lipid metabolism is tightly regulated to ensure physiological cellular processes, especially referring to crucial steps such as sperm motility, capacitation, acrosome reaction or fusion. At the same time, it has been shown that male reproductive function depends on the homeostasis of sperm lipids. Here, we review the effects of phospholipid, neutral lipid and glycolipid homeostasis on sperm fertilization function and male fertility in mammals.

Regulation of human sphingomyelin synthase 1 translation through its 5'-untranslated region

Bcr‐abl1 oncogene causes a shift in the transcription start site of the SMS1 gene (SGMS1) encoding the sphingomyelin (SM) synthesizing enzyme, sphingomyelin synthase 1 (SMS1). This results in an mRNA with a significantly shorter 5′‐UTR, called 7‐SGMS1, which is translated more efficiently than another transcript (IIb‐SGMS1) with a longer 5′UTR in Bcr‐abl1‐positive cells. Here, we determine the effects of these alternative 5′UTRs on SMS1 translation and investigate the key features underlying such regulation. First, the presence of the longer IIb 5′UTR is sufficient to greatly impair translation of a reporter gene. Deletion of the upstream open reading frame (−164 nt) or of the predicted stem‐loops in the 5′UTR of IIb‐SGMS1 has minimal effects on SGMS1 translation. Conversely, deletion of nucleotides −310 to −132 enhanced transcription of IIb‐SGMS1 to reach that of 7‐SGMS1. We thus suggest that regulatory features within nucleotides −310 and −132 modulate IIb‐SGMS1 translation efficiency.

Sphingomyelin Synthase 2 Participate in the Regulation of Sperm Motility and Apoptosis

Sphingomylin participates in sperm function in animals, and also regulates the Akt and ERK signaling pathways, both of which are associated with the asthenospermia. Sphingomyelin synthase 2 (SMS2) is involved in the biosynthesis of sphingomylin. To determine the relationship between SMS2 and human sperm function, we analyzed the distribution of SMS2 in human sperm and testes, and SMS2 expression in patients with asthenospermia and normozoospermia; human sperm were treated with anti-SMS2, and the sperm motility, penetration ability into methylcellulose, capacitation and acrosome reaction, and sperm [Ca²⁺]i imaging were evaluated, while the Akt and ERK pathway and cleaved caspase 3 were also analyzed. Results showed that SMS2 was localized in the testis and human sperm, and the protein levels of normozoospermia were higher than asthenospermia. Inhibition of SMS2 activity significantly decreased sperm motility and penetration ability into methylcellulose, but had no influence on capacitation and acrosome reaction, or on intracellular [Ca²⁺]i compared to IgG-treated control groups. Moreover, the phosphorylation level of Akt was decreased, whereas the phosphorylation of ERK and cleaved-caspase 3 levels were significantly increased. Taken together, SMS2 can affect sperm motility and penetration ability into methylcellulose, and participate in apoptosis associated with the Akt and ERK signaling pathways.

Metabolomic signature of the seminal plasma in men with severe oligoasthenospermia

BACKGROUND

Male factor is incriminated in approximately 50% of cases of infertility. The metabolomic approach has recently been used in the assessment of sperm quality and male fertility.

MATERIALS AND METHODS

We analyzed the metabolomic signatures of the seminal plasma in 20 men with severe oligoasthenospermia (prewash total motile sperm count < 5.10⁶ ) (SOA) and compared it to 20 men with normal semen parameters, with a standardized approach of targeted and quantitative metabolomics using high-performance liquid chromatography, coupled with tandem mass spectrometry, and the Biocrates Absolute IDQ p180 kit.

RESULTS

Among the 188 metabolites analyzed, 110 were accurately measured in the seminal plasma. A robust model discriminating the two populations (Q_2(cum) = 55.2%) was obtained by OPLS-DA (orthogonal partial least-squares discriminant analysis), based on the drop in concentrations of 37 metabolites with a VIP (variable important for projection) greater than 1. Overall, in men with SOA, there was a significant decrease in: 17 phosphatidylcholines and four sphingomyelins; acylcarnitines, with free L-carnitine being the most discriminating metabolite; polyunsaturated fatty acids; six amino acids (glutamate, aspartate, methionine, tryptophan, proline, and alanine); and four biogenic amines (spermine, spermidine, serotonin, and alpha-aminoadipate).

DISCUSSION

Our signature includes several metabolic changes with different impacts on the sperm quality: a change in phospholipid composition and the saturation of their fatty acids that is potentially linked to the deterioration of sperm membranes; a carnitine deficiency that can negatively impact the energy production via fatty acid oxidation and oxidative phosphorylation; and a decreased level of amino acids and biogenic amines that can lead to dysregulated metabolic and signaling pathways.

CONCLUSION

We provide a global overview of the metabolic defects contributing to the structural and functional alteration of spermatozoa in severe oligoasthenospermia. These findings offer new insights into the pathophysiology of male factor infertility that could help to develop future specific treatments.

Ceramide/Sphingomyelin Rheostat Regulated by Sphingomyelin Synthases and Chronic Diseases in Murine Models

Ceramide and sphingomyelin (SM) are major components of the double membrane-bound sphingolipids. Ceramide is an essential bioactive lipid involved in numerous cell processes including apoptosis, necrosis, and autophagy-dependent cell death. Inversely, SM regulates opposite cellular processes such as proliferation and migration by changing receptor-mediated signal transduction in the lipid microdomain. SM is generated through a transfer of phosphocholine from phosphatidylcholine to ceramide by SM synthases (SMSs). Research during the past several decades has revealed that the ceramide/SM balance in cellular membranes regulated by SMSs is important to decide the cell fate, survival, and proliferation. In addition, recent experimental studies utilizing SMS knockout mice and murine disease models provide evidence that SMS-regulated ceramide/SM balance is involved in human diseases. Here, we review the basic structural and functional characteristics of SMSs and focus on their cellular functions through the regulation of ceramide/SM balance in membrane microdomains. In addition, we present the pathological or physiological implications of SMSs by analyzing their role in SMS-knockout mice and human disease models. This review finally presents evidence indicating that the regulation of ceramide/SM balance through SMS could be a therapeutic target for human disorders.

Integrated adrenal and testicular metabolomics revealed the protective effects of Guilingji on the Kidney-Yang deficiency syndrome rats

ETHNOPHARMACOLOGICAL RELEVANCE

Guilingji (GLJ) is a well-known traditional Chinese medicine (TCM) prescription for the treatment of Kidney-Yang deficiency syndrome (KYDS).

AIM OF THE STUDY

This study aimed to address the protective effects of GLJ against KYDS in rats with pharmacodynamic indicators and target tissues (adrenal gland and testis) metabolomics.

MATERIALS AND METHODS

The rats were injected intraperitoneally (i.p) hydrocortisone to simulate KYDS and administered orally of GLJ for 30 days. Traditional pharmacodynamic indicators (body weight, behavioral indicators, biochemical parameters and histological examination) were performed to evaluate the efficacy of GLJ. Furthermore, adrenal gland and testis metabolic profiles obtained by UHPLC-Q Exactive Orbitrap-MS coupled with multivariate analysis were conducted to explore the metabolic regulation mechanism of GLJ.

RESULTS

After administration of GLJ, the weight, levels of behavioral indicators and biochemical parameters of rats were increased compared with those of the model group, and the abnormalities of morphology in adrenal and testicular tissues were improved. Furthermore, GLJ had recovering effects via the adjustment of vitamins metabolism, which was accompanied by lipids metabolism, amino acid metabolism and nucleotides metabolism.

CONCLUSIONS

The study firstly integrated the target tissues metabolic profiles, which were complementary, and GLJ had protective effects on KYDS rats via the regulation of steroid hormone biosynthesis, oxidant-antioxidant balance and energy acquisition.

Design and Synthesis of the Diazirine-based Clickable Photo-affinity Probe Targeting Sphingomyelin Synthase 2

Background:

SMS family plays a very important role in sphingolipids metabolism and is involved in the membrane mobility and signaling transduction.

Methods:

SMS2 subtype was related to a variety of diseases and could be regarded as a promising potential drug target. However, the uncertainty of the binding sites and the molecular mechanism of action limited the development of SMS2 inhibitors. Herein, we discovered a photo-affinity probe PAL-1 targeting SMS2.

Results:

The enzyme inhibitory activity and the photo-affinity labeling experiments showed that PAL-1 could be mono-labeled on SMS2.

Conclusion:

In summary, starting from the N-arylbenzamides core structure and the minimalist terminal alkyne-containing diazirine photo-crosslinker, we designed and synthesized a photoaffinity probe PAL-1 targeting SMS2. The enzymatic inhibitory activity study showed that PAL-1 exhibited superior selectivities for SMS2 with an IC50 of 0.37 µM over SMS1.

Potential therapeutic targets for atherosclerosis in sphingolipid metabolism

Sphingolipids, such as sphingomyelins, ceramides, glycosphingolipids, and sphingosine-1-phosphates (S1P) are a large group of structurally and functionally diverse molecules. Some specific species are found associated with atherogenesis and provide novel therapeutic targets. Herein, we briefly review how sphingolipids are implicated in the progression of atherosclerosis and related diseases, and then we discuss the potential therapy options by targetting several key enzymes in sphingolipid metabolism.

The Opposing Contribution of SMS1 and SMS2 to Glioma Progression and Their Value in the Therapeutic Response to 2OHOA

Background: 2-Hydroxyoleic acid (2OHOA) is particularly active against glioblastoma multiforme (GBM) and successfully finished a phase I/IIA trial in patients with glioma and other advanced solid tumors. However, its mechanism of action is not fully known. Methods: The relationship between SMS1 and SMS2 expressions (mRNA) and overall survival in 329 glioma patients was investigated, and so was the correlation between SMS expression and 2OHOA's efficacy. The opposing role of SMS isoforms in 2OHOA's mechanism of action and in GBM cell growth, differentiation and death, was studied overexpressing or silencing them in human GBM cells. Results: Patients with high-SMS1 plus low-SMS2 expression had a 5-year survival ~10-fold higher than patients with low-SMS1 plus high-SMS2 expression. SMS1 and SMS2 also had opposing effect on GBM cell survival and 2OHOA's IC₅₀ correlated with basal SMS1 levels and treatment induced changes in SMS1/SMS2 ratio. SMSs expression disparately affected 2OHOA's cancer cell proliferation, differentiation, ER-stress and autophagy. Conclusions: SMS1 and SMS2 showed opposite associations with glioma patient survival, glioma cell growth and response to 2OHOA treatment. SMSs signature could constitute a valuable prognostic biomarker, with high SMS1 and low SMS2 being a better disease prognosis. Additionally, low basal SMS1 mRNA levels predict positive response to 2OHOA.

Characterization of biological pathways associated with semen traits in the Thai multibreed dairy population

The objective of this research was to characterize biological pathways associated with semen volume (VOL), number of sperm (NS), and sperm motility (MOT) of dairy bulls in the Thai multibreed dairy population. Phenotypes for VOL (n = 13,535), NS (n = 12,773), and MOT (n = 12,660) came from 131 bulls of the Dairy Farming Promotion Organization of Thailand. Genotypic data consisted of 76,519 imputed and actual single nucleotide polymorphisms (SNP) from 72 animals. The SNP variances for VOL, NS, and MOT were estimated using a three-trait genomic-polygenic repeatability model. Fixed effects were contemporary group, ejaculate order, age of bull, ambient temperature, and heterosis. Random effects were animal additive genetic, permanent environmental, and residual. Individual SNP explaining at least 0.001% of the total genetic variance for each trait were selected to identify associated genes in the NCBI database (UMD Bos taurus 3.1 assembly) using the R package Map2NCBI. A set of 1,999 NCBI genes associated with all three semen traits was utilized for the pathway analysis conducted with the ClueGO plugin of Cytoscape using information from the Kyoto Encyclopedia of Genes and Genomes database. The pathway analysis revealed seven significant biological pathways involving 127 genes that explained 1.04% of the genetic variance for VOL, NS, and MOT. These genes were known to affect cell structure, motility, migration, proliferation, differentiation, survival, apoptosis, signal transduction, oxytocin release, calcium channel, neural development, and immune system functions related to sperm morphology and physiology during spermatogenesis.

Developmental stage-specific expression of genes for sphingomyelin synthase in rat brain

Sphingomyelin synthase genes (Sgms1 and Sgms2) encode the vital enzymes that participate in the processes of membrane transport, cell proliferation and apoptosis. We previously determined the exon-intron structure of Sgms1 and some features of its expression in human and rodent tissues. The circular RNAs (circRNAs) emerging from exons of the 5'-untranslated region (5'-UTR) of Sgms1 were determined. These circRNAs are represented at a high level in the adult brain. Here, we demonstrate that, in contrast to Sgms1, Sgms2 does not contain the multi-exon 5'-UTR but encodes circRNAs, which are composed of the coding region of the gene and are expressed at a low level. We present a study of the expression of sphingomyelin synthase genes in rat brain at embryonic days 7, 9, 13, 17 and 21 and in adult rat brain. In contrast to Sgms1, Sgms2 is expressed at a significantly low level in adult brain. In embryonic rat brain, the mRNA expression of sphingomyelin synthase genes is varied in a developmental stage-specific manner. The level of Sgms1 mRNAs, differing by 5'-UTR-in the formation of which alternative promoters can participate-changes significantly during the process of embryonic development. The expression of circRNAs of Sgms1 was significantly raised during rat embryonic brain development. We assume that the circRNAs are involved in the regulation of sphingomyelin synthase activity in rat brain in different developmental stages.